This invention describes a process for the removal or reduction in concentration of acetylene and carbon monoxide from methane and ethane. These impurities are typically found in methane and ethane that is derived from synthetic sources but may also be found in natural gas or in other gas mixtures.
These organic oxidizable impurities can be removed or reduced in concentration by a wide variety of chemical or physical procedures. Physical procedures for removal from methane are represented by distillation and adsorption. Both methods are based on equilibrium processes which require multiple steps for each additional increment of impurity removal. In addition, the physical methods generally are operated under cryogenic conditions which are comparatively costly. As a consequence, physical methods of impurity separation are terminated at an economic barrier depending on the economic advantage of removing an additional increment of impurity or at the desired methane/ethane purity level which may be beyond the economic barrier. It is particularly costly to purify methane or ethane beyond the economic barrier.
An alternative to physical methods of impurity removal from methane is the use of catalytic reduction. In this process, excess hydrogen is mixed with the impure methane stream which is then fed to a catalytic reactor in which certain of these impurities, such as olefins, may be converted to methane. This procedure does not extract the value of the impurities but does reduce their concentration. However, hydrogen is a relatively expensive material and is not always conveniently available.
In many cases the impurity level of methane and/or ethane may not affect its use and in some cases it may even be beneficial. However, in certain cases, it is important that the purity level of the methane and/or ethane be extremely high and the complete absence of these impurities is preferred. To accomplish this control of the impurity concentration via the extant physical or chemical procedures would be complicated and expensive or both. Thus it can be seen that there is a need for a less expensive method which is capable of reducing the concentration of these impurities in methane and/or ethane to very low levels.